For example, in a manufacturing process of a workpiece, more specifically, a rod-shaped workpiece having an outer peripheral surface with a circular cross section (the same applies hereinafter unless otherwise specified), for which a high mechanical strength and a high hardness are required as in a case of a rolling element such as a roller that is included in a rolling bearing, a heat treatment (quench hardening) for applying, for example, the mechanical strength required for the workpiece is carried out. The heat treatment includes, for example, a heating step of heating the workpiece being a target of the heat treatment to a target temperature and a cooling step of cooling the heated workpiece. The heating step can be carried out, for example, with use of an atmosphere heating furnace such as a mesh belt-type continuous furnace or an induction heating apparatus (for example, Patent Literature 1). In particular, with the induction heating, the following advantages are provided. Specifically, only the workpiece can be directly heated, and hence high energy efficiency can be achieved. Besides, a compact heat treatment apparatus can be achieved.
The induction heating apparatus disclosed in Patent Literature 1 includes a guide pipe as a guide member, which is configured to guide and move the workpiece along an axial direction of the workpiece, a heating coil, which is arranged on an outer periphery of the guide pipe and is configured to inductively heat the workpiece moved inside the guide pipe, and a pushing part, which is provided on an inlet side of the guide pipe and is configured to sequentially push the workpieces into the guide pipe. In this case, each of the workpieces is moved in the axial direction along with the pushing of a subsequent workpiece into the guide pipe.